"Identify the molecule" league #36. Molecule of the Year (2019/2020). Prize: knowledge + 100/20 Hive + 2000/1000 STEM + 10000/5000 CCC + 2000/1000 PAL + 2000/1000 TMN

in STEMGeeks9 months ago (edited)

This contest is an attempt to promote scientific knowledge among community in a fun and interesting way with the help of molecules.

It has been roughly 1 year since "Identify the molecule" league started.
So it's time for “The molecule of the Year” stage to happen.
You can find detailed review with all the riddles published

"Identify the molecule" league. Progress so far. “Molecule of the Year” stage is coming

Those users who won in the “Molecule of the month” stages (and previously in the corresponding week stages) (there're 4 such users) have a chance to win the following bonuses:
100 Hive, 2000 STEM, 10000 CCC, 2000 PAL and 2000 TMN;

The rest of the users have a chance to win:
20 Hive, 1000 STEM, 5000 CCC, 1000 PAL and 1000 TMN;

For more information about this contest and its rules (especially if you're new to it) read

"Identify the molecule" contest. Upgrade (the league, additional bonuses and more)


"Identify the molecule" league #30. Prize: knowledge + 5 Hive + 100 STEM + 100 CCC + 100 PAL + 200 TMN

In order to get TMN, you’ll need to have NEO-wallet and provide me your public NEO-address.
If you don’t have it yet, don’t worry, I published a post on how/where to get it (O3 wallet).
Note that NEO-addresses provided by exchanges will not work in this case (+ it's safer NOT to keep your funds on exchanges). It's highly recommended to get O3 wallet.

If there’re no winners on any stage, the bonuses will be distributed equally among all users who provided any guesses for molecules.

Even if there's a winner, all participants with guesses for molecules (not just the winners) are going to be rewarded with 20 STEM + 100 CCC + 100 PAL.


The riddle is about the family of enzymes which help organisms to synthesize an important cellular signalling molecule and can be found in vertebrates, invertebrates and bacteria.
It was discovered that mammals can produce the signalling molecule 37-39 years ago.
An amino acid, molecular oxygen, and NADPH (reduced nicotinamide-adenine-dinucleotide phosphate) serve as substrates/co-substrates for the enzyme.
And FAD/FMN (flavin adenine dinucleotide/flavin mononucleotide), and (6R-)5,6,7,8-tetrahydrobiopterin (BH4) are used as cofactors.

There're 3 isoforms/isozymes in the family, and they belong to https://enzyme.expasy.org/EC/1.14.-.-

The 1st one mostly can be found in central and peripheral nervous systems.
Its product is involved in regulation of blood pressure, learning, memory formation, and neurotransmission.

The 2nd one can be induced and found in different cells (primarily in macrophages) and helps our immune system to fight against pathogens and abnormal cells.

The 3rd isoform is mostly expressed in endothelial cells.
Its product helps to control blood pressure and vascular tone, and demonstrate a number of vasoprotective / anti-atherosclerotic effects.
All isoforms are homodimers which require haem/heme for dimerization and zinc ions for structural purpose.


(Cartoon representation. Zn2+ ions are highlighted in green, heme (4 molecules) are highlighted in white, and amino acids (substrates) are highlighted in dark grey. The image was created by me with the help of PyMol - open source tool for molecular visualization/exploration. PDB-file was obtained from PDB)


(Surface representation. Zn2+ ions are highlighted in green, heme (4 molecules) are highlighted in white, and amino acids (substrates) are highlighted in dark grey. The image was created by me with the help of PyMol - open source tool for molecular visualization/exploration. PDB-file was obtained from PDB)


Some scientists were awarded "The Nobel Prize in Physiology or Medicine" for the discovery regarding the product of the enzyme over 2 decades ago.
The molecule is smallest signalling molecule known.
The amino acid used as the substrate is L-arginine.


This contest lasts for 6 days.

Leave your guess (1 guess only (not 2 or 3+)) in the comments section of the post.

Don’t edit your comment/Don't delete or add new comments with the answers and don’t provide any evidence that your answer is correct.

The first user with correct answer is the winner.

Some of the clues have already been provided in the post.

Additional clues will be given Wednesday (20:00 ± 15 minutes UTC) (I’ll update this post).

The reason is that some people might need less information to make conclusions that the others.

Additional clues will be added at the end of the "Riddle" section before the "Rules" section with "Edited" label.

The winner will be announced on Friday, September 11, 2020, 20:00 ± 15 minutes UTC in the comments section of the next post. Plus I’ll publish a detailed review of the riddle after a while.

I’ll transfer all the tokens (and TMN, if the winner provides me his/her NEO-address) to the winner on that day.

I’m planning to run this contest every week.
So, you should expect to see the 1st week’s riddle for September on Saturday, September 12, 2020, 20:00 ± 15 minutes UTC.


I’ll add all the references for this post later, because most of them contain the name of the molecule.
That would be a spoiler.
I’ll add them after a while.


This contest is the work in progress.
A lot can be changed in the future.
Any recommendations/suggestions are very welcome.
If you have any questions, feel free to ask them in the comments section.

All images (without the license specified) are used under the doctrine known in USA as "Fair Use" (similar doctrines are used in other countries). For more information visit the US Gov website


I immediately thought of Nitric oxide synthase too but I arrived late ahah! It doesn't matter, it was fun anyway. Great contest! I wish a beautiful day to all of you :) :)

!discovery 30


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Nitric oxide synthases (NOSs)